This invention relates to the production of purified zirconium metal from zirconium ores and in particular to the portion of the process wherein purified zirconium tetrachloride is reacted with magnesium metal to reduce the zirconium tetrachloride to zirconium metal.
In the past, zirconium tetrachloride has been reduced in a batch process in a two-part vessel, with the zirconium tetrachloride to be reduced loaded into the top portion and the magnesium metal loaded in the bottom. An opening between the upper and lower portions of the reduction vessel is provided above the level of the solid zirconium tetrachloride such that when the zirconium tetrachloride is vaporized, the vapor can flow down into the lower portion of the vessel and react with the liquified magnesium.
It has been found that the prior art method has to major drawbacks. The amount of zirconium which can be produced in a single batch is severely limited by the amount of zirconium tetrachloride which can be loaded into practical size furnaces, and the quality of zirconium produced is substantially affected by the reaction rate, but the feed of zirconium tetrachloride into the bottom portion of the furnace can only be roughly controlled in such systems. This invention provides for controllably feeding as much zirconium tetrachloride as is required to produce the optimum amount of zirconium. In particular, the method controls the feed from a sublimer into the reduction vessel by using measurements indicative of the feed to control the temperature of a condenser located in conjunction with the sublimer. The condenser provides much more rapid control, as compared to attempts to control the rate at which the solid zirconium tetrachloride is heated and results in a higher quality product and allows a process control to be maintained even when additional zircionium tetrachloride is being fed into the subliming vessel.